1 package org.apache.turbine.util;
2
3 /* ====================================================================
4 * The Apache Software License, Version 1.1
5 *
6 * Copyright (c) 2001 The Apache Software Foundation. All rights
7 * reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 *
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in
18 * the documentation and/or other materials provided with the
19 * distribution.
20 *
21 * 3. The end-user documentation included with the redistribution,
22 * if any, must include the following acknowledgment:
23 * "This product includes software developed by the
24 * Apache Software Foundation (http://www.apache.org/)."
25 * Alternately, this acknowledgment may appear in the software itself,
26 * if and wherever such third-party acknowledgments normally appear.
27 *
28 * 4. The names "Apache" and "Apache Software Foundation" and
29 * "Apache Turbine" must not be used to endorse or promote products
30 * derived from this software without prior written permission. For
31 * written permission, please contact apache@apache.org.
32 *
33 * 5. Products derived from this software may not be called "Apache",
34 * "Apache Turbine", nor may "Apache" appear in their name, without
35 * prior written permission of the Apache Software Foundation.
36 *
37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48 * SUCH DAMAGE.
49 * ====================================================================
50 *
51 * This software consists of voluntary contributions made by many
52 * individuals on behalf of the Apache Software Foundation. For more
53 * information on the Apache Software Foundation, please see
54 * <http://www.apache.org/>.
55 */
56
57 import java.util.Random;
58
59 /***
60 * This class generates a unique 10+ character id. This is good for
61 * authenticating users or tracking users around.
62 *
63 * <p>This code was borrowed from Apache
64 * JServ.JServServletManager.java. It is what Apache JServ uses to
65 * generate session ids for users. Unfortunately, it was not included
66 * in Apache JServ as a class, so I had to create one here in order to
67 * use it.
68 *
69 * @author <a href="mailto:jon@clearink.com">Jon S. Stevens</a>
70 * @author <a href="mailto:neeme@one.lv">Neeme Praks</a>
71 * @version $Id: GenerateUniqueId.java,v 1.1.1.1 2001/08/16 05:09:39 jvanzyl Exp $
72 */
73 public class GenerateUniqueId
74 {
75 /*
76 * Create a suitable string for session identification. Use
77 * synchronized count and time to ensure uniqueness. Use random
78 * string to ensure the timestamp cannot be guessed by programmed
79 * attack.
80 *
81 * Format of id is <6 chars random><3 chars time><1+ char count>
82 */
83 static private int session_count = 0;
84 static private long lastTimeVal = 0;
85 static private Random randomSource = new java.util.Random();
86
87 // MAX_RADIX is 36
88
89 /*
90 * We want to have a random string with a length of 6 characters.
91 * Since we encode it BASE 36, we've to modulo it with the
92 * following value:
93 */
94 public final static long maxRandomLen = 2176782336L; // 36 ** 6
95
96 /*
97 * The session identifier must be unique within the typical
98 * lifespan of a Session; the value can roll over after that. 3
99 * characters: (this means a roll over after over a day, which is
100 * much larger than a typical lifespan)
101 */
102 public final static long maxSessionLifespanTics = 46656; // 36 ** 3
103
104 /*
105 * Millisecons between different tics. So this means that the
106 * 3-character time string has a new value every 2 seconds:
107 */
108 public final static long ticDifference = 2000;
109
110 /***
111 * Get the unique id.
112 *
113 * <p>NOTE: This must work together with
114 * get_jserv_session_balance() in jserv_balance.c
115 *
116 * @return A String with the new unique id.
117 */
118 static synchronized public String getIdentifier ()
119 {
120 StringBuffer sessionId = new StringBuffer();
121
122 // Random value.
123 long n = randomSource.nextLong();
124 if (n < 0) n = -n;
125 n %= maxRandomLen;
126
127 // Add maxLen to pad the leading characters with '0'; remove
128 // first digit with substring.
129 n += maxRandomLen;
130 sessionId.append (Long.toString(n, Character.MAX_RADIX)
131 .substring(1));
132
133 long timeVal = (System.currentTimeMillis() / ticDifference);
134
135 // Cut.
136 timeVal %= maxSessionLifespanTics;
137
138 // Padding, see above.
139 timeVal += maxSessionLifespanTics;
140
141 sessionId.append (Long.toString (timeVal, Character.MAX_RADIX)
142 .substring(1));
143
144 /*
145 * Make the string unique: append the session count since last
146 * time flip.
147 */
148
149 // Count sessions only within tics. So the 'real' session
150 // count isn't exposed to the public.
151 if (lastTimeVal != timeVal)
152 {
153 lastTimeVal = timeVal;
154 session_count = 0;
155 }
156 sessionId.append (Long.toString (++session_count,
157 Character.MAX_RADIX));
158
159 return sessionId.toString();
160 }
161
162 /***
163 * Get the unique id.
164 *
165 * @param jsIdent A String.
166 * @return A String with the new unique id.
167 */
168 synchronized public String getIdentifier(String jsIdent)
169 {
170 if (jsIdent != null && jsIdent.length() > 0)
171 {
172 return getIdentifier()+"."+jsIdent;
173 }
174 return getIdentifier();
175 }
176
177 /***
178 * Simple test of the functionality.
179 *
180 * @param args A String[] with the command line arguments.
181 */
182 public static void main(String[] args)
183 {
184 System.out.println(GenerateUniqueId.getIdentifier());
185 System.out.println(GenerateUniqueId.getIdentifier());
186 System.out.println(GenerateUniqueId.getIdentifier());
187 System.out.println(GenerateUniqueId.getIdentifier());
188 }
189 }
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